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Pharmacology: Pharmacodynamics: Paracetamol, a para-aminophenol derivative, is a peripherally acting analgesic with antipyretic and weak anti-inflammatory activity.
Orphenadrine, an analog of diphenydramine, is a skeletal muscle relaxant and is postulated to act on cerebral motor center or on the medulla through an atropine-like central action. It has anticholinergic, local anaesthetic effects and some antihistaminic effects. Orphenadrine is used either as the hydrochloride or the citrate and doses are expressed in terms of the relevant salt.
Pharmacokinetics: Paracetamol is readily absorbed from the gastrointestinal tract with peak plasma concentrations occurring about 10 minutes to 60 minutes after ingestion. It is metabolized in the liver and excreted in the urine. Less than 5% is excreted as unchanged Paracetamol. Elimination half-life varies from about 1 to 3 hours.
Orphenadrine Citrate is readily absorbed from the gastrointestinal tract. It is rapidly distributed in tissue and most of the dose is metabolized and excreted in the urine along with a small proportion of unchanged drug. A half-life of 14 hours has been reported.
